Marie-Agnès Dragon-Durey, France
Georges Pompidou European Hospital, APHP and Paris University Laboratory of ImmunologyPresenter of 1 Presentation
PRECISION OF AUTOANTIBODY ASSAYS IN THE BIOMEDICAL DIAGNOSTIC LABORATORIES: WHAT IS THE REAL LIFE?
Abstract
Background and Aims
Applying for ISO 15189 accreditation remains a real challenge for specialized laboratories. In the field of autoimmunity, beside the crucial problem linked to the absence of standardization, laboratories have to manage the analytical performances of the large panel of assays available in the market. The evaluation of such performances involves not only the clinical relevance of the assays but also their measurement precision for which no reference values are available on biorepositories.
Methods
On an initiative of the French EASI (European Autoimmunity Standardization Initiative) group, French diagnostic biomedical laboratories were proposed to participate to a survey aiming to analyze the coefficients of variation (CVs) of intra-run and inter-run variability obtained with assays quantifying 14 different autoantibodies. Two performance goals corresponding to the 90th percentile and the 50th percentile defined for three levels of concentration were calculated. The impact on the assay performances of the number of measurements, the nature of the internal quality control (IQC) and the method, were also analyzed.
Results
436 and 651 values of intra-run and inter-run CVs, respectively, were collected. The 50th percentile performance goals were comprised between 2.9% and 10.7% for the intra-run CVs, and between 2.8% and 13.2% for the inter-run CVs. CVs calculated from 10 values were similar to those obtained from more values. Higher imprecision was observed when the antibody levels of the IQC was lower than 2 fold the positive threshold.
Conclusions
Our results allow proposing some acceptability limits for the performances of the autoimmunity assays, compatible with real life in diagnostic laboratories.